The morbidity and mortality caused by essential hypertension (EH) represent major health care costs and concerns in the United States. Although there have been reductions in coronary and cerebrovascular diseases over the past few decades, much of this improvement has not been observed among blacks, especially in the "stroke belt" region of the Southeast. Blacks continue to have a greater prevalence of EH, and it is more severe. The factors which lead to the evolution of EH begin in childhood, thus we have chosen children for study. It is our goal to identify both markers for and mechanisms of evolution of EH to allow strategies to be developed for the primary prevention of EH in high-risk populations. Since blood pressure (BP) is the product of cardiac output (CO) and total peripheral vascular resistance (TPR), studies must be designed to evaluate racial differences in CO and TPR responses to challenges known to predict future BP. By the use of impedance cardiography in conjunction with BP measurement, this study seeks to define whether blacks differ from whites with respect to vasoconstrictive and/or vasodilatory function. By the incorporation of a chronic life stress inventory, the relationships between chronic stress and acute hemodynamic assessments will be determined. By use of a longitudinal study design, this investigation will determine the stability of hemodynamic responses to laboratory challenges, and the ability of either acute CO and TPR responses to laboratory stressors or changes in chronic life stress to predict future casual BP. These studies will lead to mechanistic evaluations of BP control system abnormalities to identify areas for assessment and intervention to prevent EH, especially in the high-risk black population of the United States.